clip: Rudimentary support for clip-polygon extraction

Step 1, fix the failings sighted recently by tracking clip-boxes as an
explicit property of the clipping and of composition.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 559 insertions, 0 deletions

diff --git a/src/cairo-clip-boxes.c b/src/cairo-clip-boxes.c
new file mode 100644
index 000000000..aa560ce54
--- /dev/null
+++ b/src/cairo-clip-boxes.c
@@ -0,0 +1,559 @@
+/* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */
+/* cairo - a vector graphics library with display and print output
+ *
+ * Copyright © 2002 University of Southern California
+ * Copyright © 2005 Red Hat, Inc.
+ * Copyright © 2009 Chris Wilson
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it either under the terms of the GNU Lesser General Public
+ * License version 2.1 as published by the Free Software Foundation
+ * (the "LGPL") or, at your option, under the terms of the Mozilla
+ * Public License Version 1.1 (the "MPL"). If you do not alter this
+ * notice, a recipient may use your version of this file under either
+ * the MPL or the LGPL.
+ *
+ * You should have received a copy of the LGPL along with this library
+ * in the file COPYING-LGPL-2.1; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
+ * You should have received a copy of the MPL along with this library
+ * in the file COPYING-MPL-1.1
+ *
+ * The contents of this file are subject to the Mozilla Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
+ * OF ANY KIND, either express or implied. See the LGPL or the MPL for
+ * the specific language governing rights and limitations.
+ *
+ * The Original Code is the cairo graphics library.
+ *
+ * The Initial Developer of the Original Code is University of Southern
+ * California.
+ *
+ * Contributor(s):
+ *	Carl D. Worth <cworth@cworth.org>
+ *	Kristian Høgsberg <krh@redhat.com>
+ *	Chris Wilson <chris@chris-wilson.co.uk>
+ */
+
+#include "cairoint.h"
+#include "cairo-clip-private.h"
+#include "cairo-error-private.h"
+#include "cairo-freed-pool-private.h"
+#include "cairo-gstate-private.h"
+#include "cairo-path-fixed-private.h"
+#include "cairo-pattern-private.h"
+#include "cairo-composite-rectangles-private.h"
+#include "cairo-region-private.h"
+
+static inline int
+pot (int v)
+{
+    v--;
+    v |= v >> 1;
+    v |= v >> 2;
+    v |= v >> 4;
+    v |= v >> 8;
+    v |= v >> 16;
+    v++;
+    return v;
+}
+
+
+static cairo_bool_t
+_cairo_clip_contains_rectangle_box (const cairo_clip_t *clip,
+				    const cairo_rectangle_int_t *rect,
+				    const cairo_box_t *box)
+{
+    int i;
+
+    /* clip == NULL means no clip, so the clip contains everything */
+    if (clip == NULL)
+	return TRUE;
+
+    if (_cairo_clip_is_all_clipped (clip))
+	return FALSE;
+
+    /* If we have a non-trivial path, just say no */
+    if (clip->path)
+	return FALSE;
+
+    if (clip->extents.x > rect->x ||
+	clip->extents.y > rect->y ||
+	clip->extents.x + clip->extents.width  < rect->x + rect->width ||
+	clip->extents.y + clip->extents.height < rect->y + rect->height)
+    {
+	return FALSE;
+    }
+
+    /* Check for a clip-box that wholly contains the rectangle */
+    assert (clip->num_boxes);
+    for (i = 0; i < clip->num_boxes; i++) {
+	if (box->p1.x >= clip->boxes[i].p1.x &&
+	    box->p1.y >= clip->boxes[i].p1.y &&
+	    box->p2.x <= clip->boxes[i].p2.x &&
+	    box->p2.y <= clip->boxes[i].p2.y)
+	{
+	    return TRUE;
+	}
+    }
+
+    return FALSE;
+}
+
+cairo_bool_t
+_cairo_clip_contains_box (const cairo_clip_t *clip,
+			  const cairo_box_t *box)
+{
+    cairo_rectangle_int_t rect;
+
+    _cairo_box_round_to_rectangle (box, &rect);
+    return _cairo_clip_contains_rectangle_box(clip, &rect, box);
+}
+
+cairo_bool_t
+_cairo_clip_contains_rectangle (const cairo_clip_t *clip,
+				const cairo_rectangle_int_t *rect)
+{
+    cairo_box_t box;
+
+    box.p1.x = _cairo_fixed_from_int (rect->x);
+    box.p1.y = _cairo_fixed_from_int (rect->y);
+    box.p2.x = _cairo_fixed_from_int (rect->x + rect->width);
+    box.p2.y = _cairo_fixed_from_int (rect->y + rect->height);
+
+    return _cairo_clip_contains_rectangle_box (clip, rect, &box);
+}
+
+cairo_clip_t *
+_cairo_clip_intersect_rectilinear_path (cairo_clip_t *clip,
+					const cairo_path_fixed_t *path,
+					cairo_fill_rule_t fill_rule,
+					cairo_antialias_t antialias)
+{
+    cairo_status_t status;
+    cairo_boxes_t boxes;
+
+    _cairo_boxes_init (&boxes);
+    status = _cairo_path_fixed_fill_rectilinear_to_boxes (path,
+							  fill_rule,
+							  antialias,
+							  &boxes);
+    if (likely (status == CAIRO_STATUS_SUCCESS))
+	clip = _cairo_clip_intersect_boxes (clip, &boxes);
+    else
+	clip = _cairo_clip_set_all_clipped (clip);
+    _cairo_boxes_fini (&boxes);
+
+    return clip;
+}
+
+static cairo_clip_t *
+_cairo_clip_intersect_rectangle_box (cairo_clip_t *clip,
+				     const cairo_rectangle_int_t *r,
+				     const cairo_box_t *box)
+{
+    cairo_box_t extents_box;
+    int i, j;
+
+    if (clip == NULL) {
+	clip = _cairo_clip_create ();
+	if (clip == NULL)
+	    return _cairo_clip_set_all_clipped (clip);
+
+	clip->boxes = _cairo_malloc (sizeof (cairo_box_t));
+	if (clip->boxes == NULL)
+	    return _cairo_clip_set_all_clipped (clip);
+
+	clip->extents = *r;
+	clip->num_boxes = 1;
+	clip->boxes[0] = *box;
+
+	return clip;
+    }
+
+    if (clip->num_boxes == 0) {
+	clip->boxes = _cairo_malloc (sizeof (cairo_box_t));
+	if (clip->boxes == NULL)
+	    return _cairo_clip_set_all_clipped (clip);
+
+	j = 1;
+	clip->boxes[0] = *box;
+    } else for (i = j = 0; i < clip->num_boxes; i++) {
+	cairo_box_t *b = &clip->boxes[j];
+
+	if (j != i)
+	    *b = clip->boxes[i];
+
+	if (box->p1.x > b->p1.x)
+	    b->p1.x = box->p1.x;
+	if (box->p2.x < b->p2.x)
+	    b->p2.x = box->p2.x;
+
+	if (box->p1.y > b->p1.y)
+	    b->p1.y = box->p1.y;
+	if (box->p2.y < b->p2.y)
+	    b->p2.y = box->p2.y;
+
+	j += b->p2.x > b->p1.x && b->p2.y > b->p1.y;
+    }
+    clip->num_boxes = j;
+
+    if (clip->num_boxes == 0)
+	return _cairo_clip_set_all_clipped (clip);
+
+    extents_box = clip->boxes[0];
+    for (i = 1; i < clip->num_boxes; i++) {
+	    if (clip->boxes[i].p1.x < extents_box.p1.x)
+		extents_box.p1.x = clip->boxes[i].p1.x;
+
+	    if (clip->boxes[i].p1.y < extents_box.p1.y)
+		extents_box.p1.y = clip->boxes[i].p1.y;
+
+	    if (clip->boxes[i].p2.x > extents_box.p2.x)
+		extents_box.p2.x = clip->boxes[i].p2.x;
+
+	    if (clip->boxes[i].p2.y > extents_box.p2.y)
+		extents_box.p2.y = clip->boxes[i].p2.y;
+    }
+
+    if (clip->path == NULL) {
+	_cairo_box_round_to_rectangle (&extents_box, &clip->extents);
+    } else {
+	cairo_rectangle_int_t extents_rect;
+
+	_cairo_box_round_to_rectangle (&extents_box, &extents_rect);
+	if (! _cairo_rectangle_intersect (&clip->extents, &extents_rect))
+	    return _cairo_clip_set_all_clipped (clip);
+    }
+
+    if (clip->region) {
+	cairo_region_destroy (clip->region);
+	clip->region = NULL;
+    }
+
+    clip->is_region = FALSE;
+    return clip;
+}
+
+cairo_clip_t *
+_cairo_clip_intersect_box (cairo_clip_t *clip,
+			   const cairo_box_t *box)
+{
+    cairo_rectangle_int_t r;
+
+    _cairo_box_round_to_rectangle (box, &r);
+    if (r.width == 0 || r.height == 0)
+	return _cairo_clip_set_all_clipped (clip);
+
+    return _cairo_clip_intersect_rectangle_box (clip, &r, box);
+}
+
+cairo_clip_t *
+_cairo_clip_intersect_boxes (cairo_clip_t *clip,
+			     const cairo_boxes_t *boxes)
+{
+    cairo_boxes_t clip_boxes;
+    cairo_rectangle_int_t extents;
+
+    if (boxes->num_boxes == 0)
+	return clip;
+
+    if (clip == NULL)
+	clip = _cairo_clip_create ();
+
+    if (clip->num_boxes == 0) {
+	clip->boxes = _cairo_boxes_to_array (boxes, &clip->num_boxes, TRUE);
+	_cairo_boxes_extents (boxes, &extents);
+    } else {
+	_cairo_boxes_init_for_array (&clip_boxes, clip->boxes, clip->num_boxes);
+	if (unlikely (_cairo_boxes_intersect (&clip_boxes, boxes, &clip_boxes)))
+	    return _cairo_clip_set_all_clipped (clip);
+
+	free (clip->boxes);
+	clip->boxes = _cairo_boxes_to_array (&clip_boxes, &clip->num_boxes, TRUE);
+	_cairo_boxes_extents (&clip_boxes, &extents);
+    }
+
+    if (clip->path == NULL)
+	clip->extents = extents;
+    else if (! _cairo_rectangle_intersect (&clip->extents, &extents))
+	clip = _cairo_clip_set_all_clipped (clip);
+
+    if (clip->region) {
+	cairo_region_destroy (clip->region);
+	clip->region = NULL;
+    }
+    clip->is_region = FALSE;
+
+    return clip;
+}
+
+cairo_clip_t *
+_cairo_clip_intersect_rectangle (cairo_clip_t       *clip,
+				 const cairo_rectangle_int_t *r)
+{
+    cairo_box_t box;
+
+    if (_cairo_clip_is_all_clipped (clip))
+	return clip;
+
+    if (r->width == 0 || r->height == 0)
+	return _cairo_clip_set_all_clipped (clip);
+
+    box.p1.x = _cairo_fixed_from_int (r->x);
+    box.p1.y = _cairo_fixed_from_int (r->y);
+    box.p2.x = _cairo_fixed_from_int (r->x + r->width);
+    box.p2.y = _cairo_fixed_from_int (r->y + r->height);
+
+    return _cairo_clip_intersect_rectangle_box (clip, r, &box);
+}
+
+struct reduce {
+    cairo_clip_t *clip;
+    cairo_box_t limit;
+    cairo_box_t extents;
+    cairo_bool_t inside;
+
+    cairo_point_t current_point;
+    cairo_point_t last_move_to;
+};
+
+static void
+_add_clipped_edge (struct reduce *r,
+		   const cairo_point_t *p1,
+		   const cairo_point_t *p2,
+		   int y1, int y2)
+{
+    cairo_fixed_t x;
+
+    x = _cairo_edge_compute_intersection_x_for_y (p1, p2, y1);
+    if (x < r->extents.p1.x)
+	r->extents.p1.x = x;
+
+    x = _cairo_edge_compute_intersection_x_for_y (p1, p2, y2);
+    if (x > r->extents.p2.x)
+	r->extents.p2.x = x;
+
+    if (y1 < r->extents.p1.y)
+	r->extents.p1.y = y1;
+
+    if (y2 > r->extents.p2.y)
+	r->extents.p2.y = y2;
+
+    r->inside = TRUE;
+}
+
+static void
+_add_edge (struct reduce *r,
+	   const cairo_point_t *p1,
+	   const cairo_point_t *p2)
+{
+    int top, bottom;
+    int top_y, bot_y;
+    int n;
+
+    if (p1->y < p2->y) {
+	top = p1->y;
+	bottom = p2->y;
+    } else {
+	top = p2->y;
+	bottom = p1->y;
+    }
+
+    if (bottom < r->limit.p1.y || top > r->limit.p2.y)
+	return;
+
+    if (p1->x > p2->x) {
+	const cairo_point_t *t = p1;
+	p1 = p2;
+	p2 = t;
+    }
+
+    if (p2->x <= r->limit.p1.x || p1->x >= r->limit.p2.x)
+	return;
+
+    for (n = 0; n < r->clip->num_boxes; n++) {
+	const cairo_box_t *limits = &r->clip->boxes[n];
+
+	if (bottom < limits->p1.y || top > limits->p2.y)
+	    continue;
+
+	if (p2->x <= limits->p1.x || p1->x >= limits->p2.x)
+	    continue;
+
+	if (p1->x >= limits->p1.x && p2->x <= limits->p1.x) {
+	    top_y = top;
+	    bot_y = bottom;
+	} else {
+	    int p1_y, p2_y;
+
+	    p1_y = _cairo_edge_compute_intersection_y_for_x (p1, p2,
+							     limits->p1.x);
+	    p2_y = _cairo_edge_compute_intersection_y_for_x (p1, p2,
+							     limits->p2.x);
+	    if (p1_y < p2_y) {
+		top_y = p1_y;
+		bot_y = p2_y;
+	    } else {
+		top_y = p2_y;
+		bot_y = p1_y;
+	    }
+
+	    if (top_y < top)
+		top_y = top;
+	    if (bot_y > bottom)
+		bot_y = bottom;
+	}
+
+	if (top_y < limits->p1.y)
+	    top_y = limits->p1.y;
+
+	if (bot_y > limits->p2.y)
+	    bot_y = limits->p2.y;
+	if (bot_y > top_y)
+	    _add_clipped_edge (r, p1, p2, top_y, bot_y);
+    }
+}
+
+static cairo_status_t
+_reduce_line_to (void *closure,
+		       const cairo_point_t *point)
+{
+    struct reduce *r = closure;
+
+    _add_edge (r, &r->current_point, point);
+    r->current_point = *point;
+
+    return CAIRO_STATUS_SUCCESS;
+}
+
+static cairo_status_t
+_reduce_close (void *closure)
+{
+    struct reduce *r = closure;
+
+    return _reduce_line_to (r, &r->last_move_to);
+}
+
+static cairo_status_t
+_reduce_move_to (void *closure,
+		 const cairo_point_t *point)
+{
+    struct reduce *r = closure;
+    cairo_status_t status;
+
+    /* close current subpath */
+    status = _reduce_close (closure);
+
+    /* make sure that the closure represents a degenerate path */
+    r->current_point = *point;
+    r->last_move_to = *point;
+
+    return status;
+}
+
+static cairo_clip_t *
+_cairo_clip_reduce_to_boxes (cairo_clip_t *clip)
+{
+    struct reduce r;
+    cairo_clip_path_t *clip_path;
+    cairo_status_t status;
+
+	return clip;
+    if (clip->path == NULL)
+	return clip;
+
+    r.clip = clip;
+    r.extents.p1.x = r.extents.p1.y = INT_MAX;
+    r.extents.p2.x = r.extents.p2.y = INT_MIN;
+    r.inside = FALSE;
+
+    r.limit.p1.x = _cairo_fixed_from_int (clip->extents.x);
+    r.limit.p1.y = _cairo_fixed_from_int (clip->extents.y);
+    r.limit.p2.x = _cairo_fixed_from_int (clip->extents.x + clip->extents.width);
+    r.limit.p2.y = _cairo_fixed_from_int (clip->extents.y + clip->extents.height);
+
+    clip_path = clip->path;
+    do {
+	r.current_point.x = 0;
+	r.current_point.y = 0;
+	r.last_move_to = r.current_point;
+
+	status = _cairo_path_fixed_interpret_flat (&clip_path->path,
+						   _reduce_move_to,
+						   _reduce_line_to,
+						   _reduce_close,
+						   &r,
+						   clip_path->tolerance);
+	assert (status == CAIRO_STATUS_SUCCESS);
+	_reduce_close (&r);
+    } while ((clip_path = clip_path->prev));
+
+    if (! r.inside) {
+	_cairo_clip_path_destroy (clip->path);
+	clip->path = NULL;
+    }
+
+    return _cairo_clip_intersect_box (clip, &r.extents);
+}
+
+cairo_clip_t *
+_cairo_clip_reduce_to_rectangle (const cairo_clip_t *clip,
+				 const cairo_rectangle_int_t *r)
+{
+    cairo_clip_t *copy;
+
+    if (_cairo_clip_is_all_clipped (clip))
+	return (cairo_clip_t *) clip;
+
+    if (_cairo_clip_contains_rectangle (clip, r))
+	return _cairo_clip_intersect_rectangle (NULL, r);
+
+    copy = _cairo_clip_copy_intersect_rectangle (clip, r);
+    if (_cairo_clip_is_all_clipped (copy))
+	return copy;
+
+    return _cairo_clip_reduce_to_boxes (copy);
+}
+
+cairo_clip_t *
+_cairo_clip_reduce_for_composite (const cairo_clip_t *clip,
+				  cairo_composite_rectangles_t *extents)
+{
+    const cairo_rectangle_int_t *r;
+
+    r = extents->is_bounded ? &extents->bounded : &extents->unbounded;
+    return _cairo_clip_reduce_to_rectangle (clip, r);
+}
+
+cairo_status_t
+_cairo_clip_to_boxes (cairo_clip_t *clip,
+		      cairo_boxes_t *boxes)
+{
+    _cairo_boxes_init_for_array (boxes, clip->boxes, clip->num_boxes);
+
+    if (clip->path == NULL) {
+	cairo_box_t *src = clip->boxes;
+	int i;
+
+	clip->boxes = _cairo_malloc_ab (clip->num_boxes, sizeof (cairo_box_t));
+	if (clip->boxes == NULL) {
+	    clip->boxes = src;
+	    return _cairo_error (CAIRO_STATUS_NO_MEMORY);
+	}
+
+	for (i = 0; i < clip->num_boxes; i++) {
+	    clip->boxes[i].p1.x = _cairo_fixed_floor (src[i].p1.x);
+	    clip->boxes[i].p1.y = _cairo_fixed_floor (src[i].p1.y);
+	    clip->boxes[i].p2.x = _cairo_fixed_ceil (src[i].p2.x);
+	    clip->boxes[i].p2.y = _cairo_fixed_ceil (src[i].p2.y);
+	}
+    }
+
+    return CAIRO_STATUS_SUCCESS;
+
+}